The collection of crystallographic structures related to Ebola’s GP.
Ebola virus glycoprotein (GP) is the only protein that is expressed on the surface of the virus. The GP proteins play critical roles in the entry of virus into cell and in the evasion of the immune system. The GP gene transcript to membrane GP is constituted of two subunits GP1 and GP2, and the secretory GP (sGP). The main function of GP1/2 is to attach virus to target cell’s membrane, whereas sGP has multiple functions on Ebola pathogenesis, such as inactivate neutrophils through CD16b causing lymphocyte apoptosis and vascular dysregulation. There are many studies that focused on better understanding the GP mechanism and aim at developing new antibodies and drugs such as VSV-EBOV, cAd3-EBO Z, rVSVN4CT1 VesiculoVax, ‘C-peptide’ based on the GP2 C-heptad repeat region (CHR) targeted to endosomes (Tat-Ebo) and MBX2270. In this chapter, we discuss the Ebola viral glycoproteins, genomic organization, synthesis, and their roles and functions. On the other hand, we treat the mechanisms of pathogenicity associated with Ebola GPs.
- glycoprotein (GP)
Since the beginning of the year 2012, cases of Ebola virus have been reported in four African countries: Guinea, Liberia, Sierra Leone and Nigeria. WHO announced the end of Ebola outbreak in January 2016 ; despite this, according to the WHO, new cases are declared later in Sierra Leone, Liberia and Guinea [2, 3]. What this highlights is that the risk of the Ebola epidemic is still standing. The Ebola haemorrhagic fever weans and is often fatal in humans. It is caused by
Ebola virus is a pathogenic agent of Ebola haemorrhagic fever; it is a single-stranded RNA with negative sense and with a genome length of approximately 18,920 nucleotides. Since it belongs to
The principal characteristics of the Ebola virus is the presence of a heavily glycosylated GP on the external surface of viral membrane. Crystallographic studies revealed that GP on the viral surface exists in the trimeric form .
This chapter aims to provide a current overview on the treatment of GP of the Ebola virus, genomic organization, synthesis, their roles and functions, and the mechanisms of viral entry associated with GP and replication.
2. Phylogenetic information of Ebola virus
A total of 132 sequences are collected from the NCBI gene database. The samples were collected from the Makona river (80 sequences from Sierra Leon and 52 from Guinea), and they were collected in the period between 1 June 2014 and 30 August 2015. They underwent a global alignment and phylogenetic analysis by MEGA 6.4 and BEAST [8, 9].
Phylogenetic analysis reveals a greater genetic diversity with the presence of three distinct lines. The first line represents a set of sequences found only in Guinea, and that is most closely related to viruses taken early in March 2014. The cluster found in the large Conakry region is relative to two other lines. The second cluster contains sequences from Sierra Leone and Guinea; it could be a reintroduction of Sierra Leone or Guinea streaming in related strains to those initially introduced in Sierra Leone. Finally, a third group of viruses is located in Conakry, Fore'cariah, Dalaba, and to a limited extent in Coyah. Several sequences from Sierra Leone are grouped within the third cluster. Such phylogenetic structure suggests that there have been multiple migrations of EBOV into Guinea from Sierra Leone [10, 11]. However, following the phylodynamic studies, the virus had accumulated a significant number of mutations, 7 × 10–4 substitutions per site per year . Figure 1 represents a phylogram of the Ebola virus.
3. Structural roles and genomic information on gylcoprotein
The Ebola genome mainly consists of seven genes, which encode eight proteins. Genes are delimited by conserved transcriptional signals; each gene starts with an initiation site at 3′ and ends with a (polyadenylation) stopover site. Zaire Ebola virus (EBOV) is a member of
Families of the
The common characteristics of this family are as follows: a negative genome RNA, which is linear, single-stranded, mono-segmented and filamentous; the genes in genome are ordered in specific ways, always starting with gene for envelope protein (3′UTR) and finishing with gene for the RNA polymerase (5’UTR); the viral replication occurs after synthesizing anti-genome; RNA is stored within the helical nucleocapsid; and RNA polymerase gene is the largest gene of
Besides the common characteristics, there are others that allow the distinctions between the genomes of
In Figure 2, the genome of EBOV is shown schematically. From this scheme it is evident that the fourth gene from the 3′ of the viral genome encodes for glycoprotein (GP). This gene contains two reading frames: GP is one of the genes that encode for two mRNA—ORF I of the GP gene encodes for an sGP of about 50–70 kDa (it is non-structural glycoprotein that is efficiently secreted by infected cells) and ORF II encodes for a transmembrane glycoprotein of 120–150 kDa. The length of this gene is about 2406 nucleotides and is located between nucleotide 5900 and 8308. It is located before the VP40 gene and after the VP30 gene.
The GP gene is localized between the nucleotides 5883 and 8288, where the mRNA of small non-structural secreted glycoprotein is encoded between the regions 6022 and 7116; however, the membrane GP is encoded by the regions 6022 and 8051 of nucleotides, where the region 6022–6906 is responsible for the subunit GP1 and the nucleotide sequence form 6906 to 8051 in the EBOV’s genome coding is responsible for GP2; here we observed that for sGP and GP1/2 the coding starts separately.
The GP gene advances by conserved transcription start and stop signals: “CUACUUC UAAUU” as the start transcription signal for nucleotides 5883 and 5894, and “UAAUUCU” as the stop transcription signal. The end of the gene of GP containing a region encoding (UUUUUU) or including that of the GP gene (UAAUUCUUUUU) is typically sited in the region 8278–8288. It is plausible to think that the purpose of these poly U’s into the genome, and these sites, is to form a poly-adenine during the transcription for retaining the mRNA and forming a premature protein .
A major difference between the Ebola and Marburg species has been shown with regards to the GP gene. In contrast to Ebola in which the genome contains information about two different forms of GP (sGP and GP), the GP gene of Marburg only codes a single GP.
The work of Sullivan et al.  has dismissed that a single mutation in the position 77 or 121 in the sequence of GP2 is able to influence the cytotoxicity and the immunogenicity of the virus. A post-transcriptional modification is also able to have the same effect . The post-transcriptional change may be due to the effects of prophylactic drugs or antibodies that are specifically reactive with the GP2 . The structure of EBOV GP and its interaction with the human antibody KZ52 is shown in Figure 3. Therefore, the GP1 subunit of GP binds with the GP2 subunit by a non-covalent bond; therefore, the residues of GP at the positions 266 and 476 do not significantly affect viral entry .
Multiple studies have shown that the GP gene products have the following multiple roles in the process of pathogenesis:
- The binding to the receptor is performed by the GP1 subunit whereas the GP2 subunit is responsible for the fusion and viral entry .
- Cytopathic effects: cell rounding and detachment.
- The EBOV secretory GP is incriminated in the provocation of B and T lymphoid apoptosis, but an investigation suggests that the soluble GP has no role in apoptosis . It is also involved in antigenic subversion as well as restoring the barrier function of endothelial cells .
4. Synthesis of GP and maturation
4.1. The transmembrane glycoprotein GP1/2
EBOV GP has 676 amino acids in length with an apparent molecular weight of 150 kDa. The glycoprotein is synthesized as a precursor of pre-GP (or GP0) considering the length of the gene. A series of post-translational events leads to the maturation of the viral glycoprotein,
- reduction with the availability of adhesion molecules;
- disruption of the presentation of the viral antigens to lymphocytes; and
- glycoproteins GP1 and GP2 have immunosuppressive motifs.
4.2. The secretory glycoprotein (sGP)
We hypothesize that the alteration of the homeostasis system and vascular system observed during Ebola virus disease could be, at least in part, caused by these soluble glycoproteins .
Recent works show that the source of the expression of GP1/2 or sGP is the ribosomal slippage process, where eight adenines nucleotides play an important role in the inversion of the expression of sGP and GP1/2,.If the transcription complex reads only seven adenines, it encodes for the secretory GP, while the reading of the eight adenines leads to the transcription of the pre-GP1/2 by dint of two disulphide-linked subunits GP1 and GP2. Figure 4 illustrates this translational frameshifting or ribosomal frameshifting shown in the Ebola virus GP gene .
5. Viral cycle and pathogenicity
The pathogenesis mechanism of the Ebola virus begins with the infection of the immune system’s cells such as macrophages, dendritic cells (DCs) and monocytes, which are the first that come to contact with the viral particles. An alteration of interferon’s production is observed in the infected cells, and the level of alteration is different from one cell to another. DCs and monocytes are the cells that show important level of alterations and, consequently, the INF production level decreases significantly. Furthermore, lymphocyte apoptosis and a global dysfunction of specific immune system’s cells are observed with the increase of viral burden. In addition, the virus is responsible for other dysfunctions such as neutrophils inactivation, induction of apoptosis, inhibitor of immune response, and involvement in the process of viral entry in epithelial cells, vascular dysregulation and evasion [24, 27, 28]. The spread of virus throughout the body including the vital organs with immune system dysfunction leads to death.
The Ebola virus attacks the whole body causing increasing disseminated intravascular coagulation that degrades quickly the haemostasis and the functioning of vital organs. Infection destroys the endothelial cells, mononuclear phagocytes (monocytes, macrophages, dendritic cells, mast cells) and hepatocyte . The mechanism of pathogenicity and the viral cycle can be divided into three phases:
- State extracellular and penetration, which cited the paramount role of the GP and GSP.
- State intracellular and the role of replication complex.
- Roles of VP24, VP40 and VP35 in the evasion of the immune system.
5.1. Target cells and receptors
The tropism of the Ebola virus depends on the expression of the receptor at the entry of the virus by the target cell. Several receptors of
The Ebola GP is bound to the C-type lectins as DC-SIGN, L-SIGN and hMGL expressed by monocytic, dendritic and macrophage cells [30–33]. The virus uses other ubiquitous molecules expressed by non-monocytic cells to internalize the target cells too . The Ebola virus also uses a process called antibody-dependent enhancement (ADE) to attach the host cells and facilitate the entry . It is shown that the GP binds with the IgG Fc receptor IIIb and forms a cross-linking virus-antibody-complement complex to Fcγ III, which explains the rapid spread of virus throughout the body (liver, brain, heath and endothelial cell) ; other study demonstrated that T-cell immunoglobulin and mucin domain 1 are receptors for the Ebola virus .
The Ebola virus infects most types of cells. However, macrophages and dendritic cells allow a strong replication and spread of the virus through the lymph and blood circulatory system. Thus, the virus reaches lymph nodes, liver and spleen, and spreads to other tissues.
5.2. Extracellular role of GP
The infective dose of EBOV is about 1–10 virion by aerosol in non-human primates. Despite this small amount of the virus, the formation and composition of the virion allows it to cause problems for the infected bodies.
However, after infection, it tries to prevent and interfere with the immune response via glycoproteins EBOV (GP), which is one of the reasons why the Ebola virus is fatal. The EBOV glycoprotein is the only viral protein expressed on the surface of the virion and is essential for binding to host cells and the catalysis of membrane fusion in addition to other roles of pathogenicity. The GP is combined with carbohydrates that help in the prevention of the immune system; also, the coating of the protein in a sweet layer makes it more difficult for the immune system to identify that a virus is present. On the other hand, the GP released into the intracellular medium inhibited host antibodies. It is also accompanied by the rapid neutralization of certain populations of T lymphocytes by a super-antigen effect. The GP is the essential protein in the mechanism of penetration. The GP-secreted/transmembrane GP inhibit the effect of neutralization of the natural antibodies (Ab), thanks to the carbohydrates combined with GP. The GP related to Ab easily gets attached on the cell membrane by C1q (thanks to the complement immune). This attachment facilitates and promotes deposition on host cell and this is followed by the penetration of the virus via the macropinosome pathway (this is the same capture solute of intercellular lipid lane) to the cell. Moreover, citing the possibility of using the protein G and calthrin, it indicates the role of the actin in the penetration of virus and suggests that the virus promotes, locates and retakes a large part of it action by interactions (Figure 5).
The GP binds with neutrophils and endothelial cells by the DC‑SIGN (dendritic-cell-specific ICAM3‑grabbing non-integrin) and L‑SIGN (liver and lymph node SIGN), which provide links to cell-GP via carbohydrate determinants. These bonds formed with the neutrophil receptor CD16 cause a significant reduction in the signal CR3 and Fcγ receptor II B, avoiding virus clearance. It has been shown that the strong pro-inflammatory responses were induced by the commitment of the EBOV GP with the TLR-4 and by the activation of the NF-κB transcription factor. The GP is responsible for cytotoxicity on endothelial cells by secretion of enzymes, proteolytic endosomes (such as cathepsin), that cause the destruction of the vascular endothelium and increase in vascular permeability and haemorrhagic signs.
In addition, the GP also binds with multiple nearby IgG, which allows the binding of C1 to the Fc region of antibodies that is thermo labile, and interacts with the cell surface molecules. This complex consists of C1q and two pro-enzymes of serine protease, C1r and C1s , which allow the virus to bind to cell membranes. At that time the virus enters and internalizes the cell via the macropinocytosis  (Figure 6).
The amount of BST2 into cell does not change but the surface of BST2 decreases in the presence of the GP. This explains that the GP hides the BST2 receptors in its absence, and VP40 that commune-precipitates and co-localizes binds with BST2. This reveals that GP plays a role in the inhibition of this interaction .
5.3. Intracellular action of GP
Macrophages and dendritic cells are the first to be infected, but the viruses can infect most cell types with the notable exception of lymphocytes and other non-adherent cells . Several researches have shown that the EBOV’s binding with the receptors is relatively non-specific. For example, EBOV may also attach to C-type lectins, which interact with glycans on EBOV GP as well as on phosphatidylserine (PtdSer) receptors which interacts with the viral envelope, which leads to a better EBOV entry [39, 40]. PtdSer receptors include Gas6 or protein S and TAM family receptors (TYRO3, AXL and MER).
It is suggested that EBOV enters cells through endocytosis clathrin . The typical architecture of Ebola virions (length 1–2 µm, diameter 80–100 nm) is larger than the diameter of the clathrin-coated pits (85–110 nm).
It was found that their internalization was independent of clathrin- or caveolae-mediated endocytosis, but they co-localized with sorting nexin (SNX) 5 . Once it is internalized, the virus must be carried in an intracellular compartment containing the factors essential for the activation of GP. The virus is initially inside the cell and in macropinosomes. The proteases cathepsin B and cathepsin L cysteine cleave GP and remove over 60% of the peptide mass, while interacting with NPC1 GP1 they intended to promote fusion of the viral membrane with the membrane of the bladder, accompanied with a pH drop in macropinosomes announcing the end of this step, which causes the fusion of the membrane of the host to the virus. Then, the complex transcription is released first, followed by the release of the viral genome [37, 43] (Figure 6).
Transcription and replication complex, VP35, N and L ensure the transfer of RNA– to RNA+ for transcription and translation of viral genome. The first step is the activation of the transcription complex by the fixation of zinc in the active site (70–90) of co-activator VP30. The VP30 binds with VP35, L and N to start the transcription and translation. The mRNAs are translated using host ribosomes. At this point, we can say that
The maturation of the GP track in the Golgi apparel, where the GP sequence is cleaved into GP 1 and GP2, is expressed on the surface of the cytoplasmic membrane and sGP.
The VP35, VP24 and VP40 play roles in the inhibition of immune responses by inhibition of the translation and signalization of antiviral genes by the succession of kinase-phosphorylation reactions.
When the complex polymerase binds along the RNA template, the polymerase complex stops and is re-introduced at each junction of genes and transcription, thus individual genes appear sequentially in their 3′–5′ order. The region 3′ in the genome and anti-genome viral contains promoter’s sites of replication for positive and negative sense RNA synthesis; they are approximately 176b . The virus acts on microtubules and immunosuppressive genes to inhibit cell division. As the number of virions increases, it causes a burst of the host cell and then death or apoptosis due to the speed of the replication of virions, which are approximately 109 plaque-forming units (PFUs) in tissue during 7–10 days .
The spread of the virus in the body and vital organs causes haemorrhage and fever due to unskilled hyper activation of cytokines via transmembrane GP, and the activity of the NK causes diarrhoea because of the infection of digestive cells of the system. In addition, the pneumocystis, hepatocytes and cardiovascular cell infection accelerates the death of the patient.
5.4. Strategies for the inhibition of the
Several methods can be used to inhibit
6. Biosecurity, biosafety and Ebola virus
A good understanding of the mechanisms of the virus’ action allows us to manipulate the viruses in the level of biosafety, which is lower than BSL-4. The virus is composed of two complementary and essential units for the infectious act, genome and VP30, VP35, VP40 and L proteins; merging of genome with these four proteins is capable of inducing infection. As Ebola is a negative sense single-stranded RNA virus, the isolation of their genome from its microenvironment composed of four proteins cannot trigger a viral reaction. As such Ebola cannot synthesize DNA genome, therefore, its cDNA copy is synthesized only in a laboratory, in which all manipulation conditions are easily manageable.
The best way to master and control the transcription and translation processes in the laboratory is by not allowing a transcription/translation of the total genome. Moreover, by isolating the proteins from their genome and other proteins, the pathogenic effects can be stopped. The pathogenic effect is caused by the cooperation and integration of different proteins that make up the genome of the viruses; however, the loss of a single protein causes the inhibition of virus by losing their genetic information via the degradation of cellular RNA as in the case of VP30.
It is possible to clone cDNA in
Based on the data presented in this chapter, Ebola has developed multiple pathways and modes for the evasion of the immune system and internalization in target cells. Further studies are necessary for a good understanding of the entry mechanism. However, the specific proteins of virus or even the cDNA genome disassociated of proteins can be studied in BSL-2 because the effects of virus depends on the presence of genome associated with structural and functional proteins, which allows to study the virus in laboratories at biosafety level 3 or 2. They may even accelerate the process of finding new inhibitors by pharmaceutical and vaccination companies.
The authors thank the Ministry of Higher Education, University Hassan II of Casablanca, Faculty of Sciences and Technics and the Laboratory of Virology, Microbiology, Quality and Biotechnologies/Ecotoxicology & Biodiversity-Team of Virology, oncology and medical Biotechnologies.
http://www.who.int/mediacentre/news/releases/2016/ebola-zero-liberia/en/consulted, 20 April 2016.
Gatherer, D. The 2014 Ebola virus disease outbreak in West Africa, published online ahead of print May 2, 2014. DOI: 10.1099/vir.0.067199-0, J Gen Virol May 2014 Vir.0.067199-0, Received 22 April 2014. Accepted 28 April 2014.
Geisbert, T. W., & Jahrling, P. B. (1995). Differentiation of Filoviruses by electron microscopy. Virus Research 39(2–3): 129–150. PMID 8837880.
De la Vega, M. A., Wong, G., Kobinger, G. P., & Qiu, X. (2015). The multiple roles of SGP in Ebola pathogenesis. Viral Immunology, 28(1): 3–9.
Lee, J. E., Fusco, M. L., Hessell, A. J., Oswald, W. B., Burton, D. R., & Saphire, E. O. (2008). Structure of the Ebola virus glycoprotein bound to an antibody from a human survivor. Nature, 454(7201): 177–182.
Drummond, A. J., Suchard, M. A., Xie, D., & Rambaut, .A (2012). Bayesian phylogenetics with BEAUti and the BEAST 1.7. Molecular Biology and Evolution 29: 1969–1973. Full text.
Tamura, K., Dudley, J., Nei, M., & Kumar, S. (2007). MEGA4: Molecular Evolutionary Genetics Analysis (MEGA) software version 4.0. Molecular Biology and Evolution 24: 1596–1599. (Publication PDF at http://www.kumarlab.net/publications).
Baize, S., Pannetier, D., Oestereich, L., Rieger, T., Koivogui, L., Magassouba, N. F., … & Tiffany, A. (2014). Emergence of Zaire Ebola virus disease in Guinea. New England Journal of Medicine, 371(15), 1418-1425.
Dudas G, Rambaut A (2014) A phylogenetic analysis of Guinea 2014 EBOV Ebolavirus outbreak. PLoS Curr 6: 1229–123
Carroll, S. A., et al. (2013). Molecular evolution of viruses of the family Filoviridae based on 97 whole-genome sequences. Journal of Virology. 87: 2608–2616. DOI:10.1128/JVI.03118-12
King, A. M. Q., Adams, M. J., Carstens, E. B., & Lefkowitz, E. J. (2011). The international code of virus classification and nomenclature. In: King, A. M. Q., Adams, M. J., Carstens, E. B., & Lefko-Witz, E. J. (editors). Virus taxonomy—Ninth Report of the International Committee on Taxonomy of Viruses. Elsevier/Academic Press, London, pp. 1273–1277.
Kuhn, J. H., Becker, S., Ebihara, H., Geisbert, T. W., Johnson, K. M., Kawaoka, Y., Lipkin, W. I., Negredo, A. I., Netesov, S. V., Nichol, S. T., Palacios, G., Peters, C. J., Ten-Orio, A., Volchkov, V. E., Jahrling, P. B. (2010). Proposal for a revised taxonomy of the family filoviridae: classification, names of taxa and viruses, and virus abbreviations. Archives of Virology 155 (12): 2083–2103. DOI: 10.1007/S00705-010-0814-X. PMC 3074192. PMID 21046175
Bukreyev, A. A., Chandran, K., Dolnik, O., Dye, J. M., Ebihara, H., Leroy, E. M.,… & Kuhn, J. H. (2014). Discussions and decisions of the 2012–2014 International Committee on Taxonomy of Viruses (ICTV) Filoviridae Study Group, January 2012–June 2013. Archives of Virology, 159(4): 821–830.
Pringle, C. R. (1997). The order mononegavirales-current status. Archives of Virology 142.11: 2321–2326.
Bukreyev, A. A., Belanov, E. F., Blinov, V. M., & Netesov, S. V. (1995). Complete nucleotide sequences of Marburg virus genes 5 and 6 encoding vp30 and vp24 proteins. Biochemistry and Molecular Biology International 35: 605–613.
Sanchez, A., Kiley, M. P., Klenk, H. D., & Feldmann, H. (1992). Sequence analysis of the mar-burg virus nucleoprotein gene: comparison to Ebola virus and other non-segmented negative-strand RNA viruses. Journal of General Virology 73: 347–357.
Volchkova, V. A., Vorac, J., Repiquet-paire, L., Lawrence, P., & Volchkov, V. E. (2015). Ebola virus GP gene polyadenylation versus RNA editing. Journal of Infectious Diseases, JIV150.
Sullivan, N., Chakrabarti, B., Yang, Z. Y., Pau, M. G., Goudsmit, J., & Nabel, G. (2015). U.S. Patent No. 9,012,618. Washington, DC: U.S. Patent and Trademark Office.
Manicassamy, B., Wang, J., Jiang, H., & Rong, L. (2005). Comprehensive analysis of Ebola virus GP1 in viral entry. Journal of Virology, 79(8): 4793–4805.
Takada, A., Robison, C., Goto, H., Sanchez, A., Murti, K. G., Whitt, M. A., & Kawaoka, Y. (1997). A system for functional analysis of Ebola virus glycoprotein. Proceedings of the National Academy of Sciences USA 94: 14764–14769.
Russier, M. (2013). Cellules NK et fievres hemorragiques virales: etude de leur role dans la mise en place des reponses immunes et dans la pathogenese lors de l'infec-tion par les virus lassa et ebola. Doctoral Dissertation, ecole normale superieure de lyon-ens Lyon.
Escudero-perez, B., Volchkova, V. A., Dolnik, O., Lawrence, P., & Volchkov, V. E. (2014). Shed GP of Ebola virus triggers immune activation and increased vascular permeability. PLOS Pathogens 10(11): e1004509.
Mohan, G. S., Li, W., Ye, L., Compans, R. W., & Yang, C. (2012). Antigenic subversion: a novel mechanism of host immune evasion by Ebola virus. PLoS Pathogens 8(12): e1003065.
Mohamadzadeh, M., Chen, L., & Schmaljohn, A. L. (2007). How Ebola and Mar-burg viruses battle the immune system. Nature Reviews Immunology 7(7): 556–567.
Mohamadzadeh, M., Coberley, S. S., Olinger, G. G., Kalina, W. V., Ruthel, G., Fuller, C. L.,… & Schmaljohn, A. L. (2006). Activation of triggering receptor ex-pressed on myeloid cells-1 on human neutrophils by Marburg and Ebola viruses. Journal of Virology 80(14): 7235–7244.
Geisbert, T. W., Young, H. A., Jahrling, P. B., Davis, K. J., Kagan, E., & Hensley, L. E. (2003). Mecha-nisms underlying coagulation abnormalities in Ebola hemorrhagic fever: overexpression of tissue factor in primate mono-cytes/macrophages is a key event. Journal of Infectious Diseases 188(11): 1618–1629.
Garcia-vallejo, J. J., & Van Kooyk, Y. (2015). DC-sign. C-type lectin with prominent role in immune system. In Glycoscience: Biology and Medicine (pp. 649–659). Springer, Japan.
Gillespie, L., Roosendahl, P., Ng, W. C., Brooks, A. G., Reading, P. C., & Londrigan, S. L. (2016). Endocytic function is critical for influenza a virus infection via DC-sign and l-sign. Scientific Reports, 6: 19428.
Wang, H., Shi, Y., Song, J., Qi, J., Lu, G., Yan, J., & Gao, G. f. (2016). Ebola viral gly-coprotein bound to its endosomal receptor Niemann-Pick C1. Cell 164(1): 258–268.
Takada, A., Fujioka, K., Tsuiji, M., Morikawa, A., Higashi, N., Ebihara, H.,… & Kawaoka, Y. (2004). Human macrophage c-type lectin specific for galactose and n-acetylgalactosamine promotes filo-virus entry. Journal of Virology 78(6): 2943–2947.
Zampieri, C. A., Sullivan, N. J., & Nabel, G. J. (2007). Immunopathology of highly virulent pathogens: insights from Ebola virus. Nature Immunology 8(11): 1159–1164.
Brudner, M., Karpel, M., Lear, C., Chen, L., Yantosca, L. M., Scully, C.,… & Mungall, B. A. (2013). Lectin-dependent enhancement of Ebola virus infection via soluble and transmembrane c-type lectin receptors. PLoS One 8(4), e60838.
Sui, J., & Marasco, W. A. (2002). Evidence against Ebola virus SGP binding to human neutrophils by a specific receptor. Virology 303(1): 9–14.
Kondratowicz, A. S., Lennemann, N. J., Sinn, P. L., Davey, R. A., Hunt, C. L., et al. (2011). T-cell immunoglobulin and mucin domain 1 (TIM-1) is a receptor for Zaire Ebola virus and lake Victoria Marburgvirus. Proceedings of the National Academy of Sciences U S A. doi: 10.1073/pnas.1019030108
Takada, A., Feldmann, H., Ksiazek, T., & Kawaoka, Y. (2003). Antibody-dependent enhancement of Ebola virus infection. Journal of Virology, 77(13): 7539–7544.
Gustin, J. K., Bai, Y., Moses, A. V., & Douglas, J. L. (2015). Ebola virus glycoprotein promotes enhanced viral egress by preventing Ebola vp40 from associating with the host restriction factor bst2/tetherin. Journal of Infectious Diseases, JIV125.
Dube, D., et al. (2010). Cell adhesion-dependent membrane trafficking of a binding part-ner for the Ebola virus glycoprotein is a determinant of viral entry. Proceedings of the National Academy of Sciences USA 107: 16637–16642.
Moller-tank, S., & Maury, W. (2014). Phosphatidylserine receptors: enhancers of enveloped virus entry and infection. Virology 468–470c: 565–580.
Mollertank, S., & Maury, W. (2015). Ebola virus entry: a curious and complex series of events. PLOS Pathogens, 11(4): e1004731.
Nanbo, A., Imai, M., Watanabe, S., Noda, T., Takahashi, K., Neumann, G.,…& Kawaoka, Y. (2010). Ebolavirusis internalized into host cells via macropinocytosis in a viral glycoprotein-dependent manner. PLoS Pathogens 6(9): e1001121.
White, J. M., & Schornberg, K. L. (2012). A new player in the puzzle of filovirus en-try. Nature Reviews Microbiology 10(5): 317–322.
Kondratowicz, A. S., Lennemann, N. J., Sinn, P. l., Davey, R. A., Hunt, C. L., Mollertank, S., Meyerholz, D. K., Rennert, P., Mullins, R. F., Brindley, M., Sandersfeld, L. M., Quinn, K., Weller, M., Mccray, P. B., Chiorini, J., & Maury, W. (May 2011). "T-cell immunoglobulin and mucin domain 1 (TIM-1) is a receptor for Zaire Ebola virus and lake victoria marburgvirus". Proceedings of the National Academy of Sciences U.S.A. 108(20): 8426–8431. doi:10.1073/pnas.1019030108. pmc 3100998. pmid 21536871.
http://viralzone.expasy.org/all_by_species/5016.html, consulted 4th April 2016.
Mühlberger, E. 2007. Filovirus replication and transcription. Future Virol. 2:205–215
Higgins, C. D., Koellhoffer, J. F., Chandran, K., & Lai, J. R. (2013). C-peptide inhibitors of Ebola virus glycoprotein-mediated cell entry: effects of conjugation to cholesterol and side chain–side chain crosslinking. Bioorganic & Medicinal Chemistry Letters 23(19): 5356–5360.
Bukreyev, A., Volchkov, V. E., Blinov, V. M., & Netesov, S. V. (1993). The GP-protein of Marburg virus contains the region similar to the ’immunosuppressive domain’ of oncogenic retrovirus p15 e proteins. FEBS Lettters 323: 183–187.
Empig, C. J., & Goldsmith, M. A. (2002). Association of the caveola vesicular system with cellular entry by Filoviruses. Journal of Virology 76: 5266–5270.
Wolf, K., Beimforde, N., Falzarano, D., Feldmann, H., & Schnittler, H. J. (2011). The Ebola virus soluble glycoprotein (sGP) does not affect lymphocyte apoptosis and adhesion to activated endothelium. Journal of Infectious Diseases 204(Suppl 3): S947–S952.
Ravikiran, T., & Prasad, Y. (2014). Ebola virus disease: epidemic broke out in lateral Africa. Indo American Journal of Pharmaceutical Research 4(12): 5909–5918.
Heinz Feldmann, “Ebola virus cDNA and the NIH guidelines for Ebola virus cDNA and the NIH guidelines for research involving recombinant DNA molecules research involving recombinant DNA molecules”, National Institutes of Health (NIH) Recombinant DNA Advisory Committee (RAC) 116th Meeting Tuesday, March 3–4, 2009
Michael Buchmeier, “Ebola cDNA: Biosafety Risks and Biosecurity Concerns”, National Institutes of Health (NIH) Recombinant DNA Advisory Committee (RAC) 116th Meeting Tuesday, March 3–4, 2009